I'm by no means an "expert" but this is what I do for flats..
Yellow mustard all over
Sprinkle rub all over
Wrap in plastic wrap and put in fridge
Put on smoker at 225-250 degrees until internal hits 160.
Take off. Wrap in foil with a little beer.
Put back on. Take off when it hits 190 internal
Put in a cooler to let rest for a few hours.
Its worked well for me in the past. And by "in the past" I mean I've done it once and got great reviews.
1 - Ducane Gas Grill ~ 1 - WSM 22.5 ~ 1 Char Griller Akorn